The broad research objectives are concerned with investigations at the molecular-biochemical level of the mechanism of RNA tumor virus replication and cell transformation. The specific aim will be directed toward the elucidation of the following area: Transcription in vitro of 60S virus RNA catalyzed by purified AMV reverse transcriptase with particular emphasis on obtaining large DNA products biologically active from oncornavirus RNA. Large DNA transcripts will be used to synthesize double-stranded "DNA provirus" which could be used in structural studies with known sequence specific restriction enzymes.